The present invention relates to conveyor belt scraper blade assemblies and, more particularly, to scraper blade assemblies adapted to clean older conveyor belts.
Conveyor belt assemblies of the type having a flexible, endless belt are frequently used in mining operations to convey abrasive, particulate material. After long periods of use, the flexible belt, which may be a fabric coated with rubber or polyvinyl chloride, tends to stretch and wear such that the load-carrying surface of the belt assumes a concave contour across its width. This occurs in part because such belt systems employ troughed idlers to support the belt so that it has a concave shape in use to concentrate the load in the middle of the belt. This troughing effect causes the belt fabric to stretch along its middle.
When such belts are used to carry particulate material which may be wetted, accumulations of material build up on the belt. Such accumulations are removed by conveyor belt scrapers such as that shown in Stoll U.S. Pat. No. 4,402,394, which is commonly assigned. Such conveyor belt scrapers include one or more scraper blades, each having an elongate scraping blade surface which is urged into contact with the load-carrying surface of the conveyor belt, preferably on a return run of the conveyor apparatus. The scraping surfaces of such blades are generally flat in shape, and therefore are unable to conform to the concave contour of a worn conveyor belt in order to remove accumulations of material from the central portion of the belt.
Attempts have been made to develop conveyor belt scrapers which are capable of conforming to the contour of the conveyor belt. Such an apparatus is exemplified by the blade shown in Matson U.S. Pat. No. 3,504,786. That patent shows a conveyor belt scraper assembly which comprises a plurality of scraper blade segments which are mounted on the ends of rods attached to a bar spanning the width of the conveyor belt and mounted on a support which rotates the bar to urge the blades into contact with the belt. The blade segments are each sized and positioned to extend across only a part of the belt, and the rods are sufficiently flexible so that the blade segments are individually biased to engage an associated part of the belt, whether the belt is substantially flat in contour or has a convex shape.
A disadvantage with such designs is that the large number of parts required to fabricate such an assembly results in an increased cost of production and high maintenance costs. Furthermore, the use of individual blade segments which are urged into the load-carrying surface of the belt by resilient rods often results in the "chattering" of the blade segment, during which it bounces into and out of contact with the belt surface. This substantially reduces the efficiency of the blade scraper since the individual scraper elements are in contact with the load-carrying surface on a less-than-constant basis during use.
Accordingly, there is a need for a conveyor belt scraper blade assembly which is capable of conforming to the concave contour of a worn conveyor belt, and which is relatively low-cost and does not have a high maintenance requirements. There is also a need for a conveyor belt scaper blade assembly which reduces the likelihood of blade chatter, and therefore increases the efficiency of material removed.